STANFORD, Calif. (AP)—American teenager Madison Keys wandered around the Stanford University campus wondering what it would have been like had she chosen school over tennis.

This would have been her freshman year.

"I could be going to college soon," Keys said. "I'm pretty happy where I am."

Keys, one of 11 Americans ranked in the top 100, beat No. 8 seed Magalena Rybarikova 6-2, 6-2, in the first round of the $795,000 Bank of the West Classic on Monday.

Her likely major? "Something that doesn't have math it," she said.

Keys, ranked a career-high 44th, played a typical match in topping the 39th-ranked Slovakian for the second time in three career meetings.

Keys recorded four aces and had three double faults. She won 70 percent of her first serve points. In 40 previous matches this season, the 18-year-old phenom averaged 3.8 aces and 1.35 double faults per match while winning 69.7 percent of her first-serve points.

"I had a little bit of nerves," Keys said. "The court was really fast and I tried to get used to it. It was also the first tournament on hardcourt and I'm always nervous at the beginning of a tournament."

She's still looking for her first WTA Tour title, but she's had her moments in her career.

A few months after turning pro on her 14th birthday, she beat Serena Williams 5-1 in a World Team Tennis match. She's 6-5 in Grand Slam events, reaching the third round at both the Australian Open and Wimbledon.

In her last match, Keys took Wimbledon finalist Agnieszka Radwanska to three sets at the All-England Club.

"That gave me a lot of confidence," she said. "I realized afterward that I had played well and that made me want to work that much harder."

Keys did take some time off after Wimbledon, spending time with relatives and hitting the beach.

"I got to have four whole days of summer," she said. "But I was also happy to get back to tennis."